The purpose of this study is to evaluate the effectiveness and safety of a dermally applied testosterone gel preparation in hypogonadal men treated daily for six months. Effectiveness will be determined on the basis of circulating testosterone concentrations and pharmacological response to testosterone (e.g. gonadotropin suppression, bone formation markers, muscle strength, body composition, and libido) compared to patients treated daily with a nonscrotal testosterone transdermal patch that is already marketed.